Wax impregnated leather and method of making same



United States atent'O WAX INIPREGNATED LEATHER AND METHOD OF MAKING SAME Application November 21, 1952, Serial No. 321,954

3 Claims. (Cl. 117-55) No Drawing.

This invention relates to 2. treated leather and the method of making it. The invention relates more particularly to making leather Weatherproof but vapor and air permeable, resistant to loss of these properties on dry cleaning, and resistant to soiling and staining during use and retentive of pliability after being washed with soap and water and subsequently dried.

The need of such a product is long standing. When it has been attempted heretofore to make a weatherproof suede, for instance, it has been necessary to compromise on something less than the complete set of desirable properties stated above.

This invention provides a treated leather having the desirable properties stated and in which the coloring material is not subject to being rubbed off, the dyes do not bleed when wet with rain, cutting resistance isincreased thus giving evidence of increased durability of the leather itself, and fibers hold together so that the leather may be split into lesser thicknesses than heretofore possible for equal strength of product in processing and use.

Our new leather contains a wax composition extending through the leather from face to back and so fixed in position that it resists removal by dry cleaning. The improved retention for the Wax or resistance to removal by dry cleaning solvents is illustrated by the following data showing the effect of dry cleaning on the water resistance. With the impregnation of skins by a Wax and zirconium salt complex, without special pretreatment of the skins, three dry cleanings reduce the water repellency by as much as 50% as measured by the standard spray test method for determining water repellency. With our improved product pretreated with an emulsion of a surface active penetrating agent and subsequent washing with water, before introduction of the wax complex, three dry cleanings reduce the water repellency by not more than o.

Briefly stated, our invention comprises the method of and the product resulting from introducing into skins, as after tanning and fat liquoring, an aqueous emulsion of a dispersion (either a solution or a colloidal dispersion) of a surface active penetrating agent in a water immiscible volatile solvent, and then introducing into the skins an emulsified mixture of a wax and a zirconium salt or the like.

GENERAL METHOD In general the method of treating the leather is as follows:

Skins, after the tanning and fat liquoring steps are pretreated by being tumbled in a drum with an aqueous emulsion of a solution of a surface active penetrating agent in a volatile solvent therefor that is immiscible in water. At a later stage of their processing and after treatment with water or an aqueous solution, such as a dye bath, the skins are partially dried and dipped briefly in an emulsified mixture of a wax, emulsifying agent, and a zirconium salt or the like in water. The resulting treated skins are then pulled out and dried, as at 80 to 130 F. In this method there is a remarkably rapid rate of penetration of the emulsified wax mixture into the pretreated skins. Immersion of the pretreated skins in the emulsified Wax mixture for approximately 1-2 seconds is adequate to give the desired product in which the wax complex penetrates throughthe skin from face to back and is so anchored or fixed that the product resists removal of wax by dry cleaning solvents and gives the other desirable properties of the product that have been described.

It is considered that the emulsion of the penetrating agent and organic solvent, in the penetration and subsequent removal by water, removes oily material originally present in the skins and places the fine capillaries therein in condition to receive and hold the wax emulsion subsequently applied.

MATERIALS The leather being made may be of any usual kind, as for example, that from the skins of sheep, goat, pig, deer, cow or calf. a

The surface active penetrating agent used in the solvent emulsified with water for the pretreatment must be one that does not affect color or the handle of the finished leather adversely, is compatible with sulfonated sperm oil or other fat liquoring materials in amount that is left in the skin after fat liquoring, and is an emulsifying agent for water immiscible solvents in water. We avoid cationic surfactants for most purposes and use surfactants that are anionic or non-anionic. Examples of surface active penetrating agents that meet these general requirements and that are satisfactory are the following:

Sodium salt of sulfonated isopropyl oleate (Duofol AS3).

Sodium salt of sulfated monoethanolamide of coconut oil fatty acids (Hytergen GL 10).

Sodium salt of sulfonated octyl sulfosuccinic acid (Decersol).

Sodium keryl benzene sulfonated (Ultra Wet).

Alkyl phenol ether of polyethylene glycol (Triton X), as, for example, dissobutyl phenol ether of polyethylene glycol 400.

Polyethylene glycol thioether of alkyl mercaptan (Nonic 218), as for instance, the polyethylene glycol 400 thioether of dodecyl mercaptan.

Akylene oxide derivative of partial esters of higher fatty acids wtih polyhydric alcohols (Spans or Tweens) as, for example, the derivative of sorbitol monolaurate containing 25 ethoxy groups.

Polyethylene glycol 400 monolaurate.

The solvent used for the surface active penetrating agent 'is one that is water immiscible and volatile. .Examples of such solvents that we use are carbontetrachloride, perchlorethylene, kerosene, naphtha, toluol, xylol and mixtures of two or moreof these or likeliquid or. ganic solvents.

The wax used in the subsequent treatment of the skin is a water insoluble and water repellent wax of which examples are paraffin, carnauba, bees, and candililla wax.

As the emulsifier for the wax we use any one of those emulsifiers which are common for emulsifying wax in water. Examples are morpholineoleate, the ammonium salt of cottonseed oil fatty acids, and the aminomethyl propanol salt of oleic acid, used alone or in mixtures with each other. t

As the metal compound in the wax emulsion, we use one of the polyvalent metals commonly employed in emulsions of complexes of the selected wax. Zirconium in the form of a salt serves this purpose well. We find no overall advantage in replacing the zirconium salt by the salt of any other metal but we do obtain somewhat better results'in the use of zirconium salt in conjunction with a salt of aluminum. In any case the metal selected for use should be in the form of a salt of relatively low acidity in water. Examples of such salts that we use are zirconium oxychloride, acetate, or formate and aluminum acetate or formate.

As to proportions, the penetrating agent in the pretreating emulsion is used in amount to give the desired penetrating effect. This requires aminimum of about 0.115% of the weight of the emulsion. We use from this amount up to approximately 0.5% above which proportion there is not a compensating gain to offset the extra cost of unnecessary penetrating agent.

The proportion of the solvent used to dissolve the penetrating agent is ordinarily 2 to 5 times the proportion of the said agent. Of the whole aqueous emulsion of the solvent and agent, the solvent and agent together suitably constitute about 0.5 to 5%. The whole emulsion is used in quantity to wet through the skins being treated. This requires ordinarily about 75 to 150 parts of the emulsion for 150 parts" of the skins on the dry basis.

The emulsified mixture of wax-metal complex and water used for the after treatment of the skins will contain about 0.2% -0.8% of the wax, about a tenth as much morpholine oleate or like emulsifying agent, and about 1 to 4 times as much of the metal salt, the remainder being w ter- When the skin is soaked in this emulsified mixture, the skin takes up about its own weight of the mixture so that the rest of the emulsion applied may be drained away from the skin.

As to conditions of treatment, the various steps in the conversion of skins to leather are conventional except as stated herein, the term skins being used to include hides and partly finished leather.

The skins are treated with the emulsion of the solution of the surfactant at a pH that is 4-6 for best commercial results. When the pH is substantially below 4, then the acidity causes some deterioration of the skins. When the pH is much above 6, there is bleeding of the wood extract previously introduced as tanning material. For the same reasons the pH at the time of treatment with the emulsified Wax mixture is also within about the range 46, a pH above 6 at this stage being objectionable also as causing some bleeding of color which is introduced previous to the wax treatment.-

Temperatures are kept at all times below 135- -F. in order'to avoidheat deterioration of the skins and the loss ofoilsl The temperature at the time of the wax'treatment is kept somewhat elevated to prevent precipitation of wax on the surface of the leather. When parafiin wax is used, for instance, the temperature is'kept above 120 F. but not above 135 F. and for best operations around 130 F.

To make the emulsified wax mixture, the wax and emulsifying agent are dispersed in' warm water such as water at 130 F. After this dispersion is efiected, then the selectedzirconium or other polyvalent salt or mixture is introduced. If this order of mixing is reversed, the wax emulsion breaks. l

The invention will be further illustrated by description in connection with the following specific examples of the practice of it. In these examples and elsewhere herein proportions are expressed as parts by weight.

Example 1 Sheep skins are tanned and fat-liquored in the usual way. The skins are then subjected to a pretreatment by being tumbled in an aqueous emulsion of a solution of Duofol AS in kerosene and trichlorethylene containing about 4% on the, weight of the pickled skins of the Duofol AS, 0.2% of deo dorized kerosene, and /2% of trichlorethylene, at a pH of 4.5. The temperature of the emulsion is brought to 130? F. in a drum and the skins are run in the drum for 20 to 30 minutes, so that the penetrating agent Duofol AS penetrates through the skins. The skins are then removed from the drum, horsed up and set out, and then hung up to dry at a temperature of 130 F. for a period of 8 to 10 hours. The skins are then wet back at to F. in .a drum with .water and sufficient borax to bring the pH of the solution to 6 to 7. The skins are then dyed in usual manner, as with acidic, basic, or direct dyes. The dyes are then set with formic acid solution at a pH of 4 to 5. The skins are removed from the dyeing bath and set out to a moisture content of 30% to 40% of the weight of the skins on the dry basis.

An emulsified Wax mixture is then prepared, in a vat equipped with stainless steel heating coils and agitator, from 200 ga'lcns of water to which is added 65 pounds of a parafiiu wax and Water emulsion containing 20% wax of melting point 128130 F. and 2% of morpholine oleate as the emulsifying agent. There are then added to the mixture 130 pounds of an aqueous solution containing 13% of zirconium oxychloride and 36% of aluminum formate brought to a pH of 5 with ammonia. The resulting whole emulsified mixture or bath is kept agitated and is brought to a temperature of 130 F.

The skins are dipped into the emulsified wax mixture, 1 to 2 seconds being adequate for penetration and subsequent fixing of the wax and zirconium complex within the skins. The skins are then removed from the bath and horsed up. They are then set out and hung to dry at 130 F. The thus dried skins are then napped and finished in the normal procedure for finishing suede.

Example 2 The procedure of Example 1 is followed except that the wax used consists of a mixture of 80% parafiin wax and 20% refined carnauba wax and the mixed zirconium and aluminum salts are replaced by zirconium oxychloride alone in proportion equal to 75% of the combined weight of the zirconium and aluminum salts in Example 1.

Example 3 The procedure of either Example 1 or 2 above is followed with the substitution of the sheep skins by any of the other skins listed herein and/ or by the substitution of any of the solvents, surface active penetrating agents, waxes, or emulsifying agents listed herein for the representatives of those classes of materials used in Example 1 or 2. Products made as described are characterized by water repellency and resistance to extraction of the wax by dry cleaning solvents that normally extract the wax rapidly, as shown by tests reported above, by permeability to air and vapor of water or the likeas shown by evaporation occurring through shoe leather made as described, retention of pliability after washing with soap and water, followed by drying, and resistance to soiling and staining. When tomato juice and ink were poured on our processed leather and rinsed off no stain remained.

It will be understood that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the, purpose of illustration which do not constitute departures from the spirit and scope of the invention.

What we claim is:

1. In making leather from skins that have been tanned and fat-liquored, the process which comprises applying to the skins, at a pH of about 4-6, an aqueous emulsion consisting essentially of a dispersion of a surface active, non-cationic penetrating agentin a volatile solvent that is immiscible with water, subjecting the thus treated skins to an elevated temperature to remove water and solvent by evaporation thereof, and then applying thereover an emulsified mixture of a water insoluble Wax, an emulsifying agent, and a zirconium salt in water, removing the excess of unabsorbed emulsified mixture from the skins, and drying the resulting product, this method giving a vapor permeable, water repellent, and soil and stain re-, sistant product.

2. The method of claim 1 in is parafiin wax.

3. Leather comprising tannedv and .fat-liquored skins which the said wax used and wax and zirconium salt complex extending through the skin from face to back, the leather being characterized by water repellency, resistance to soiling and staining, permeability to air and vapor of water and the like, retention of pliability after washing with soap and Water and subsequent drying, and resistance of the wax complex to removal by dry cleaning solvents and being the product of the method of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS Teague Feb. 28, 1933 Muller Mar. 28, 1944 Wilson June 24, 1952 Figdor Apr. 14, 1953 FOREIGN PATENTS Great Britain Nov. 28, 1932 

1. IN MAKING LEATHER FROM SKINS THAT HAVE BEEN TANNED AND FAT-LIQUORED, THE PROCESS WHICH COMPRISES APPLYING TO THE SKINS, AT A PH OF ABOUT 4-6, AN AQUEOUS EMULSION CONSISTING ESSENTIALLY OF A DISPERSION OF A SURFACE ACTIVE, NON-CATIONIC PENETRATING AGENT IN A VOLATILE SOLVENT THAT IS IMMISCIBLE WITH WATER, SUBJECTING THE THUS TREATED SKINS TO AN ELEVATED TEMPERATURE TO REMOVE WATER AND SOLVENT BY EVAPORATION THEREOF, AND THEN APPLYING THEREOVER AN EMULSIFIED MIXTURE OF A WATER INSOLUBLE WAX, AN EMULSIFYING AGENT, AND A ZIRCONIUM SALT IN WATER, REMOVING THE EXCESS OF UNASBORBED EMULSIFIED MIXTURE FROM THE SKINS, AND DRYING THE RESULTING PRODUCTS, THIS METHOD GIVING A VAPOR PERMEABLE, WATER REPELLENT, AND SOIL AND STAIN RESISTANT PRODUCT. 